The present invention relates to a semiconductor device and a process for producing the same. More particularly, the present invention pertains to a technique for improving heat dissipating characteristics of semiconductor devices.
Considerations of thermal design in semiconductor devices are very important. Thermal design is particularly important to multichip modules involving relatively large power dissipation such as those which have a plurality of semiconductor elements (chips), e.g., IC's and LSI's, mounted thereon.
One example of the structure for such multichip module will be explained through a multichip module which has already been proposed by the applicant of the present invention.
More specifically, the prior art multichip module has the following structure. A chip (referred to as a "mother chip" in this case) which is defined by a wiring board formed by providing a multilayer wiring structure on a silicon substrate is rigidly secured to the lower surface of a board of a package. A multiplicity of chips (referred to as "child chips" in this case) defined by semiconductor elements such as IC's or LSI's are rigidly secured to the lower surface of the mother chip, the child chips being electrically connected by so-called CCB (controlled collapse bonding). Leads for external connection are interposed between the package board and a cap for the package. The mother chip and the leads are electrically connected, i.e., wired by connecting wires, and fins for heat dissipation are attached to the upper surface of the package board.
Bump electrodes made of solder are generally employed for the CCB electrical connection employed for electrical wiring between the chips. It should be noted that the bump electrodes include electrically conductive bumps for transferring electric signals between the mother chips and the child chips, and heat-dissipating bumps (dummy bumps) for merely dissipating the heat generated in the child chips to the external environment through the mother chip and then the heat-dissipating fins. The heat-dissipating bumps maintain electrical insulation between the mother chip and the child chips, and while doing so, they transfer the heat from the child chips to the mother chip and dissipate the transferred heat to the external environment. Accordingly, an insulator film for electrical insulation is provided directly below a portion of each heat-dissipating bump which is in contact with either the mother chip or a child chip.
The insulator film provided directly below a heat-dissipating bump electrode has heretofore been defined by a film generally made of silicon oxide SiO.sub.2, silicon nitride Si.sub.3 N.sub.4 or the like. For this reason, this insulator film is inferior in terms of thermal conductivity, and since the heat-dissipating bump electrode is interposed, the thermal resistance at this electrode portion is disadvantageously high, which is a problem in terms of heat-dissipating characteristics of multichip modules of the type described above, particularly high-power multichip modules.